A First Insight Into Object-Aware Hardware Transactional Memory

The contribution of this paper is the first Hardware Transactional Memory (HTM) where the object structure is recognized and harnessed. Our approach is similar to hardware support of paged virtual memory using a virtually addressed cache and a TLB, and is based on a cache hierarchy that allows the addressing of objects by unique object identifiers. The object-aware HTM allows cache overflows of uncommitted data. It also enables a novel commit and conflict detection mechanism. In this preliminary evaluation, the Lee-TM application exhibits overflows that in most previous HTMs would have had to be handled by software, impacting on performance. The simulation provides an insight into the scalability characteristics of the proposed HTM, which uses object and field granularity, lazy versioning and lazy conflict detection. For example, with 32 cores the broadcast of write sets is at under 5% of the bus bandwidth, showing the potential of object-aware HTM systems.